Elevated fasting plasma C-peptide occurs in non-diabetic individuals with fatty liver, irrespective of insulin resistance

Serum C-X-C motif chemokine ligand 14 levels are associated with serum C-peptide and fatty liver index in type 2 diabetes mellitus patients

AIMS/INTRODUCTION

Recent studies have suggested C-X-C motif chemokine ligand 14 (CXCL14), secreted from adipose tissue, to play an important role in the pathogenesis of metabolic syndrome. However, the clinical significance of CXCL14 in humans has not been elucidated. This study aimed to assess correlations between serum CXCL14 levels and clinical parameters in patients with type 2 diabetes mellitus.

MATERIALS AND METHODS

In total, 176 individuals with type 2 diabetes mellitus were recruited. Serum CXCL14 concentrations were determined by enzyme-linked immunosorbent assay. We examined the associations of serum CXCL14 levels with laboratory values, abdominal computed tomography image information, surrogate markers used for evaluating the pathological states of diabetes, obesity and atherosclerosis.

RESULTS

Serum CXCL14 levels correlated positively with body mass index, waist circumference, subcutaneous and visceral fat areas, and serum alanine transaminase, uric acid, total cholesterol, low-density lipoprotein cholesterol, triglycerides and C-peptide (CPR) levels. In contrast, CXCL14 levels correlated inversely with age, pulse wave velocity and serum adiponectin levels. Multiple linear regression analysis showed serum levels of CPR (β = 0.227, P = 0.038) and the fatty liver index (β = 0.205, P = 0.049) to be the only parameters showing independent statistically significant associations with serum CXCL14 levels.

CONCLUSIONS

Serum CXCL14 levels were independently associated with serum CPR and fatty liver index in patients with type 2 diabetes mellitus. In these patients, a high serum CPR concentration might reflect insulin resistance rather than β-cell function, because CXCL14 showed simple correlations with obesity-related parameters. Collectively, these data suggested that serum CXCL14 levels in type 2 diabetes patients might be useful predictors of elevated serum CPR and hepatic steatosis.

Long-term effects of increased protein intake after weight loss on intrahepatic lipid content and implications for insulin sensitivity: a PREVIEW study

The aim of this study was to assess the effects of a weight maintenance period comprising two diets differing in protein intake, after weight loss, on intrahepatic lipid content and implications for insulin sensitivity. A total of 25 participants [body mass index (BMI): 31.1 (3.5 kg/m²; intrahepatic lipid (IHL): 8.7 (8.3%; fasting glucose: 6.4 (0.6 mmol/l; homeostatic model assessment for insulin resistance (HOMA-IR): 3.7 (1.6; Matsuda index: 3.4 (2.9] started an 8-wk low-energy diet followed by a 2-yr weight maintenance period with either high protein or medium protein dietary guidelines. At baseline, after 6 mo, and after 2 yr, IHL, visceral adipose tissue (VAT), and subcutaneous adipose tissue (SAT) were determined by magnetic resonance spectroscopy/imaging. Glucose and insulin concentrations, determined during an oral glucose challenge, were used to assess the HOMA-IR and Matsuda insulin sensitivity index (ISI). Protein intake was measured with 24-h urinary nitrogen excretion. Protein intake, BMI, IHL, VAT, SAT, HOMA-IR, and ISI did not change differently between the groups during the intervention. In the whole group, BMI, IHL, VAT, SAT, HOMA-IR, and ISI were favorably changed at 6 mo and 2 yr compared with baseline ( P < 0.05). Mixed-model analysis showed that independent of BMI, protein intake (g/d) at 6 mo was inversely related to IHL (coefficient: -0.04; P < 0.05) and VAT (coefficient: -0.01; P < 0.05). Overall, IHL was positively related to HOMA-IR (coefficient: 0.10; P < 0.01) and inversely related to ISI (coefficient: -0.17; P < 0.01), independent of BMI. A 2-yr medium- to high-protein energy-restricted diet reduced IHL and VAT. Independently of changes in BMI, IHL was inversely related to insulin sensitivity.

NAFLD/NASH in patients with type 2 diabetes and related treatment options

Type 2 diabetes may reduce life expectancy and patients' quality of life due to its micro- and macro-vascular complications and to the higher risk of several types of cancer. An emerging important factor is represented by the hepatic involvement; it is recognized that excessive hepatic fat accumulation represents a typical feature of diabetic patients and that it also plays an important pathogenic role. It is now evident that non-alcoholic fatty liver disease (NAFLD), generally perceived as a benign condition, may have on the contrary an important deleterious impact for diabetic patients increasing the risk to develop cardiovascular complications but also serious hepatic diseases, in particular non-alcoholic steatohepatitis (NASH), cirrhosis and hepatocellular carcinoma. Lifestyle intervention, bariatric surgery and several drug therapies have now accumulated evidence of efficacy in treating NASH. On the other hand, their durability and safety in the long-term is yet to be proven and their use may be sometimes associated with side effects or higher risk of adverse events limiting the regular administration or contraindicating it. Professional health care providers, building awareness about the importance of these hepatic complications, should put more efforts in primary prevention using a behavioral therapy needing a multidisciplinary approach, in secondary prevention applying on a regular basis in the clinical setting available predictive algorithms to identify the patients at higher cardiovascular and hepatologic risk, and in tertiary prevention treating, when not contraindicated, the diabetic patients preferentially with drugs with proven benefit on NAFLD/NASH.

Lean Seafood Intake Reduces Postprandial C-peptide and Lactate Concentrations in Healthy Adults in a Randomized Controlled Trial with a Crossover Design

BACKGROUND

Recently we showed that lean seafood consumption reduced circulating triacylglycerol (TG) and VLDL concentrations and prevented an elevated total-to-HDL-cholesterol ratio relative to intake of a nonseafood diet.

OBJECTIVE

We aimed to elucidate whether diet-induced altered carbohydrate metabolism could be a contributing factor to the previously observed different lipoprotein patterns.

METHODS

This was a secondary outcome and explorative randomized controlled trial with a crossover design in 20 healthy adults (7 men and 13 women) that were 50.6 ± 3.4 (mean ± SEM) y old, weighed 75.7 ± 2.5 kg, and had a body mass index (BMI, in kg/m(2)) of 25.6 ± 0.7. After a 3-wk run-in period and separated by a 5-wk wash-out period, the participants consumed 2 balanced diets [in percentage of energy (energy%); 29% fat, 52% carbohydrates, 19% protein] for 4 wk. The diets varied in the main protein sources; 60 energy% of total protein was from either lean seafood or nonseafood sources. On the first and last day of each diet period, fasting and postprandial blood samples were collected before and after consumption of test meals (in energy%; 28% fat, 52% carbohydrates, 20% protein) with cod or lean beef.

RESULTS

The diets did not alter serum insulin and glucose concentrations. However, relative to the nonseafood diet period, the lean seafood diet period reduced postprandial C-peptide (P = 0.04) and lactate (P = 0.012) concentrations and fasting and postprandial TG/HDL-cholesterol ratios (P = 0.002). Hence, different postprandial lactate levels occurred at equal glucose concentrations.

CONCLUSIONS

Even though the diets did not alter serum insulin and glucose concentrations, intake of the lean seafood compared with the nonseafood diet reduced postprandial concentrations of C-peptide and lactate and the TG/HDL-cholesterol ratio in healthy adults in a manner that may affect the long-term development of insulin resistance, type 2 diabetes, and cardiovascular disease. This trial was registered at www.clinicaltrials.gov as NCT01708681.

Why does NAFLD predict type 2 diabetes?

Based on the "lipotoxic" hypothesis, the free fatty acid flux from the excessive amount of adipose tissue toward the peripheral tissues would induce the development of insulin resistance especially when the triglyceride storage or the concentration of intermediate fat metabolites (diacylglycerides, ceramides) within the cytoplasm of these cells become excessive. Nonalcoholic fatty liver disease (NAFLD) includes a wide spectrum of liver damage, ranging from simple steatosis to steatohepatitis and advanced fibrosis. NAFLD is associated with general and intra-abdominal obesity and with a reduced ability of insulin to stimulate metabolic pathways in the liver itself and in other tissues. There are animal models and models in human diseases sustaining the hypothesis that a primary hepatic disease may determine the development of type 2 diabetes (T2DM). Epidemiologic data generated on surrogate markers of NAFLD (transaminases and γ-glutamyltransferase), semiquantitative assessment of fatty liver (ultrasound), and surrogate algorithms of NAFLD also support a causative effect of NAFLD on the risk to develop T2DM. In spite of the presence of these indirect associations, a clear-cut link between NAFLD and abnormal β-cell function is yet to be reported. Therefore, more data are warranted to prove what is considered a likely causative relationship between NAFLD and T2DM.